Data storage systems use magnetic or other media for storage of digital information. For example, typical disc drives use rigid or flexible discs coated with a magnetizable medium for storing information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g., air) bearing disc head sliders. The sliders carry transducers, which write information to and/or read information from the disc surface. An actuator mechanism moves the sliders from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a suspension for each slider. The suspension includes a load beam and a gimbal. The load beam provides a load force, which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a slider body having a bearing surface, such as an air bearing surface, which faces the disc surface. As the disc rotates, the air pressure between the disc and the air bearing surface increases and creates a hydrodynamic lifting force, which causes the slider to lift and fly above the disc surface. The preload force supplied by the load beam counteracts the hydrodynamic lifting force. The preload force and the hydrodynamic lifting force reach an equilibrium, which determines the flying height of the slider relative to the disc surface.
In some applications, the slider flies in close proximity to the surface of the disc. This type of slider is known as a “pseudo-contact” slider, since the bearing surface of the slider can occasionally contact the surface roughness of the disc. In other applications, the slider is designed to remain in direct contact with the disc surface with substantially no air bearing. These sliders are referred to as “contact recording” sliders. The transducer is typically mounted at or near the trailing edge of the slider so that it is located near the closest point on the slider body to the media.
A thin film type of transducer is a microstructure that is designed to perform certain electric, electromagnetic or optical functions during reading and/or writing. Thin film transducers are typically fabricated in an array on an active surface of a wafer substrate through a series of material deposition, etching and liftoff process steps. The wafer substrate is typically made of a ceramic material. Once the array of transducers has been fabricated, the wafer substrate is divided into a number of individual slider bodies. Each slider is thus composed of a ceramic body and a thin film transducer on one side of the body.
During operation, the distance between the active element of the transducer structure, such as the pole tips in a magnetic write transducer, and the media is known as the “head-media spacing”. As the recording densities of data storage systems continue to increase, it is important to maintain a substantially constant head-media spacing during operation and to have tight control over the head-media spacing from one slider to the next during fabrication.
In addition to the flying characteristics of the slider, the head-media spacing depends on the vertical position of the pole tip (or other active element) on the slider body. Two primary factors contribute to the pole tip position. The first is pole tip recession (PTR), in which the vertical position of the pole tip becomes recessed relative to the bearing surface due to the machining and other fabrication processes of the slider and transducer structures. The second is thermal pole tip protrusion (TPTP), which is caused by increases in the environmental temperature of the product and by heat generated by the write current through the transducer during normal operation. Manufacturing variations in pole tip recession therefore contribute to undesirable variations in head-media spacing, which can limit recording density.
The present invention provides a solution to this and other problems and offers other advantages over the prior art.